1. Field of the Invention
The present invention relates to an internet protocol (IP) phone system and to a control method for an IP phone system which gives an IP address to an IP phone device and obtains the IP address from the IP phone device.
Priority is claimed on Japanese Patent Application No. 2004-078293, filed Mar. 18, 2004, the content of which is incorporated herein by reference.
2. Description of Related Art
In recent years, internet protocol (IP) phones which use voIP (voice over Internet Protocol) which is a technology for performing a voice telephone call on an IP network such as an Internet, an Intranet, or the like is quickly spreading.
Here, when the IP phone device which is connected to the Intranet (the local network) communicates with an IP phone device other than the IP phone device on the Internet, or with the other IP phone device on the other Intranet via the Internet, a transformation processing between a local IP address used in the Intranet and a global IP address used on the Internet occurs.
This is because the Internet and the Intranet use different IP address systems (spaces), and thereby the Internet and the Intranet manage the addresses on each network.
Usually, the transformation processing is performed at the boundary of the Intranet and the Internet by a router which relays packets.
The transformation processing is performed in order to effectively use the IP address resources, which are limited, and is a NAT (Network Address Translation) processing or a NAPT (Network Address Port Translation) processing which is the extended version thereof.
The specific NAT processing which is mentioned above is briefly explained as follows.
When the packets of the sound signal are transmitted from the first IP phone device which is connected to the Intranet to the second IP phone device which is connected to the other network via the Internet, the IP address which is located in the address section of the caller of the packets is rewritten from the local IP address of the first IP phone device to the IP address at the side of the Internet which is held in the router, that is, the global IP address.
Moreover, regarding the packets of the sound signal which are transmitted from the second IP phone device via the Internet, the IP address at the side of the Intranet which is held in the router is rewritten in the address section of the caller.
As mentioned above, excessive communication time will be taken and excessive delay will arise in the case of transmitting of the packets by rewriting processing of the IP address in the packets.
In order to avoid such a delay, as prior art in connection with the IP address transformation processing at the time of the voice telephone call, there is the method which is proposed in Japanese Unexamined Patent Application, First Publication No. 2001-156852 (Patent Document 1).
In this method, the router, which performs the NAT processing, becomes the broker for both parties to the call (the above-mentioned first and second IP phone devices) at the stage of the call setting of the telephone call, acts as the representative of the two parties, and has the two telephone call parties set so that the packets of the sound signal come to the place of the router.
Furthermore, the router rewrites the communication port number and the IP address to which the packets are transmitted on the basis of the IP address and the port number of the two telephone call parties which were acquired for the packets of the sound signal in the call setting stage by the router (for example, see Patent Document 1).
However, in this method, delay of the sound signal will arise because IP address conversion is performed for not only the packets of call setting but also for the packets of the sound signal.
Therefore, the above-mentioned prior art has a problem in that the real time performance of the sound signal is lost, as compared with the telephone call which is performed between the IP phone devices which hold the global IP addresses (that is, the case in which the IP address conversion is not performed.
As one of the solutions of this problem, it is possible to originally give the global IP addresses to all IP phones, and to make the IP address conversion unnecessary.
However, the global IP address is a limited resource, even if the address space uses IPv6 (IP version6) which is 128 bits.
For example, an action in which various controlling is attempted to perform for not only the IP phone but also the home electronic appliance from the exterior via the Internet occurs; therefore, in the case in which each global IP address is corresponded to each home electronic appliance at each home, a limit will also arise using IPv6.
That is, as the number of apparatuses which are connected to the IP network increase, the problem of the IP address running out has occurred.
The right of using of the global IP addresses has been already assigned to each country by IANA (Internet Assigned Numbers Authority).
Furthermore, the assigning processing which assigns the global IP addresses which are assigned by IANA to the company or the organization of each country by the management organization of each country is further performed in order to manage the global IP addresses in the country.
For example, in Japan, CORPORATION AGGREGATE JPNIC (Japan Network Information Center) performs the assigning processing in which the global IP addresses which are assigned to Japan are assigned to the applicants of a domestic global IP addresses.
Therefore, in the case in which an applicant who acquires a global IP address is an enterprise which affords the IP phone service to unspecified customers, the enterprise deployment will be projected within the number of the global IP addresses which are assigned from JPNIC to the enterprise.
However, as the number of the customers who use the IP phones increases, the demand for the global IP addresses which are used in order to connect the IP phones also increases.
As a result, because the number of the global IP addresses which are assigned is limited, as described above, there is a limit in assigning the global IP address to each IP phone.